Sloshing of viscous liquids within launch vehicle tanks is a recurring issue when using liquid propellant engines. Many launch vehicles, from the Soviet N-1 lunar rocket to the French Emeraude series, have failed due to sloshing phenomena. Two main mechanisms are involved. The first is known as the "Pogo effect," a feedback loop involving propulsion, structural dynamics, and the movement of fluids within the tanks. During flight, propellant sloshing causes pressure fluctuations in the tanks, which in turn disrupt the engine’s fuel supply and lead to thrust oscillations. These oscillations generate structural vibrations in the launcher, which further amplify the sloshing. If this feedback becomes constructive, it can lead to severe damage or even total destruction of the vehicle. The second phenomenon involves lateral forces and torques induced by sloshing, which can destabilize the flight trajectory and potentially lead to mission failure. Mitigating sloshing in launch vehicles is therefore a critical challenge in aerospace engineering.
My research on this topic began during my Bachelor's thesis with the EPFL Rocket Team, a student association dedicated to designing rockets for inter-university competitions. In 2021, the team began developing rockets powered by bipropellant engines, which brought sloshing issues to the forefront. My task was to find a method to mitigate sloshing without resorting to structural modifications of the tanks—an industry-standard solution that was too costly for a student team. Our research therefore focused on biphasic liquid sloshing. We discovered that most of the viscous energy dissipation due to sloshing occurs within the top 10% of the tank volume. By using a biphasic liquid system, where the upper phase is highly viscous yet relatively small in volume, we achieved significant attenuation of sloshing.
To address concerns about the purity of fuel required for combustion, we devised an approach in which beads represent a highly viscous phase floating above the main fuel phase. Laboratory experiments showed that the presence of a bead layer on the surface of a liquid effectively damps oscillations. However, resonance can still occur through small gaps in the bead layer, allowing localized liquid oscillations to propagate rapidly throughout the tank. A sufficient quantity of beads is necessary to maintain a continuous, compact layer and prevent these discontinuities.
Following these lab tests, I designed an experiment with the Rocket Team’s payload division. The setup was integrated into a 3-unit CanSat format, which was embedded in the supersonic rocket "Wildhorn", developed by the same team. The goal was to test this sloshing mitigation strategy under real flight conditions. The rocket was launched, and the results from this experiment are currently being analyzed.
In parallel, I independently developed and experimentally validated a theoretical model describing the sloshing of a viscous fluid in a rectangular tank. This work, conducted in collaboration with Benjamin Meunier and Professor Daniele Mari, is currently under publication.
[Back to Homepage]List of publications
- Study of Faraday waves in tanks in presence of polystyrene bead layers, Emergent Scientist 7 (2023), Maxime C.N. Roux, Benjamin A.H. Meunier and Daniele Mari, (DOI)
- Sloshing of viscous fluids: Application to aerospace, arXiv (2021), Benjamin A.H. Meunier and Maxime C.N. Roux, (DOI)
List of talks
- 73rd International Astronautical Congress, Paris, September 2022 : Characterization of the dampening of liquid sloshing with foam-like materials, Loup Cordey, Maxime C.N. Roux and all, (abstract)